Introduction

1. Introduction • Grew up in Northern California • B.S. in Computer Science and Math from Chico • 15 years with Hewlett-Packard • CEO of tecBugs: GIS on the web • Ph.D. from Colorado State University • Research Scientist with the Natural Resource Ecology Laboratory • Visiting Professor at Oregon State University

2. Geospatial Science Teaching • Introduction through Advanced GIS • GIS Programming • Design of GIS Systems • Spatial Modeling • Modeling species movements in space and time • Environmental impacts

3. Forestry Wildlife Geology Fisheries Recreation Engineering Environmental Management Policy Restoration Education Engineering What are you interested in?

4. Chapter 3 • Geodesy, Datums, Map Projections, • and Coordinate Systems: • Ellipsoid • Geoid • Geographic coordinates: • latitude and longitude • Horizontal datums • Commonly used datums • Datum transformations

5. Geodesy • The science of measuring the shape of the Earth, and map projections, the transformation of coordinate locations from the Earth’s curved surface onto flat maps. NOAA NOAA NOAA

6. Coordinates • Must accurately and repeatedly locate spatial data on the earth • Problems: • The earth is not flat • The earth is not a perfect sphere • There are different versions of the earth’s shape • Measurements always have error Oldest known world map, 6th century BC Babylonia.

7. USGS Benchmarks

8. USGS Benchmarks • Benchmark shapefiles by state: http://www.ngs.noaa.gov/cgi-bin/sf_archive.prl http://fatwaramdani.wordpress.com NOAA, City of Arcata, NationalAltas.gov

9. Peak of Founder’s Hall • Google Earth, 2012 • DOQQ 1993 USGS Benchmark: NAD83 -124.07745, 40.87714 or 40 52 37.69549 N, 124 04 38.81922 W

10. The Earth is Not A Sphere! • Earth is like a big bag of molten lava spinning out its axis • Not Spherical, an “oblate spheroid” or “ellipsoid” 12, 756 km “Molten” 12, 714 km

11. Shape of the Earth Eratosthenes (date) 6406km in radius Today: 6,378km

12. Shape of the Ellipsoid • Circumference of the earth: • 40,075km • Radius at Equator, Semi-Major: • a=6,378,137.0 (~6,378km) • Radius at Poles, Semi-Minor: • b=6,356,752.3 (~6,356km) • Flattened at the poles by about: • Flattening = a-b = 21384.7 (~21km) • Flattening Factor = (a-b)/a = 0.00335270 • Inverse Flattening = a/(a-b) = 298.267

13. Major Axis Minor Axis Flattening = Semi-Major Axis/ (Semi-Major Axis – Semi-Minor Axis)

15. GIS Fundamentals, Paul Bolstad, University of Minnesota

16. Datum • Horizontal Reference • Based on an ellipsoid (modern) • Includes: • Name: GCS_WGS_1984 • Spheroid: • Semi-Major Axis: 6378137.0 (Polar Radius) • Flattening: 298.257223563

17. Common Datums • NAD27 • NAD83 (1986) • NAD83 (HARN) • NAD83 (CORS96) • NAD83 (2007) • WGS72 • WGS84 (G1150) Up to 100 meter difference <2 meter differences

18. North-South Datum Shift

19. East-West Datum Shift

20. ArcGIS Datum Shifts • Picture of ArcGIS with geographic transform menu

21. Selecting a Datum Shift • Block on selecting transformation: • http://blogs.esri.com/esri/arcgis/2009/05/06/about-geographic-transformations-and-how-to-choose-the-right-one/ • Article with tables to select datum shift for each version of ArcGIS: • http://support.esri.com/en/knowledgebase/techarticles/detail/21327 • SEER Web Site with EPSG Database: • http://seer.science.oregonstate.edu

22. Geographic/Datum Transforms • International Association of Oil and Gas Producers: • European Petroleum Survey Group (EPSG) • http://www.epsg.org/ • 53 Ellipsoids • 630 Datums (Ellipsoid plus prime meridian and units)

23. Geoid – Based on Gravity Exagerated Geoid – follows mean sea level NOAA

24. Geoids vs. Ellipsoids Spirit level used in traditional surveying follows the Geoid Mean Sea level follows geoid principles.ou.edu

25. Geoids Vs. Ellipsoids

26. Vertical Datums • National Geodetic Vertical Datum of 1929 (NGVD 29). • Assumed water level is equal all along the coast, this created errors • North American Vertical Datum of 1988 (NAVD 88), more accurate, resulting in a difference of minus 1.51 feet • Vertical Datum Conversion Software VERTCON http://www.ngs.noaa.gov/datums/vertical/VerticalDatums.shtml

27. Spherical Coordinates • Longitude: • Degrees East or West from the prime meridian • Latitude: • Degrees North or South from the Equator Point of Interest Latitude Longitude

28. Longitude: -180° to 180° -180° 180° North Pole EAST WEST -90° 90° Prime Meridian 0° Polar View

29. Longitude: 180° W to 180° E 180° W 180° E Pole EAST 90° E WEST 90° W Prime Meridian 0° Polar View

30. Longitude: 0° to 360° 180° Pole EAST 90° 270° WEST Prime Meridian 360° 0° Polar View

31. Latitude: 90° to -90° 90° ~40° Equator 0° -90° Equatorial View

32. Latitude: 90°N to 90°S 90° N ~40°N Equator 0° 90° S Equatorial View

33. Lines of Longitude Lines of Longitude Meridians Prime Meridian Greenwich, England 0º 0º -45º 45º 67.5º -90º -67.5º 90º -22.5º 22.5º

34. Lines of Latitude Lines of Latitude Parallels 90º 67.5º 45º Equator 0º 22.5º 0º -22.5º -45º -67.5º -90º

36. Magnetic vs. Geographic • Magnetic North • Point at the north pole where compass needles point • Based on the earth’s magnetic field • Geographic North • Point that all modern maps use as north • Based on the rotation of the earth • There is also a magnetic south pole and geographic south pole

37. Geographic Coordinates